Washington, March 16 (Reuters): A spacecraft orbiting Mars has scanned huge deposits of water ice at its south pole so plentiful they would blanket the planet in 11 meters of water if they were liquid, scientists said yesterday.

The scientists used a joint Nasa-Italian Space Agency radar instrument on the European Space Agency Mars Express spacecraft to gauge the thickness and volume of ice deposits at the Martian south pole covering an area larger than Texas.

The deposits, up to 3.7 km thick, are under a polar cap of white frozen carbon dioxide and water, and appear to be composed of at least 90 percent frozen water, with dust mixed in, according to findings published in the journal Science.

Scientists have known that water exists in frozen form at the Martian poles, but this research produced the most accurate measurements of just how much there is.

They are eager to learn about the history of water on Mars because water is fundamental to the question of whether the planet has ever harboured microbial life. Liquid water is a necessity for life as we know it.

Jeffrey Plaut of Nasas Jet Propulsion Laboratory in Pasadena, California, who led the study, said the same techniques are being used to examine similar ice deposits at the Martian north pole.